Polyethylene polymers, blends thereof with other polymers, and articles made therefrom are generally known in the art. Many varieties of polyethylene polymers have been prepared over the years, including those made using high pressure free radical chemistry (LDPE), traditional linear low density polyethylene (LLDPE) typically made using Ziegler-Natta processes, and polyethylene made by metallocene or other catalysts. Generally, polyethylenes made by different processes have different molecular architectures and distribution characteristics giving rise to varying positives and negatives, depending on application or end-use.
One way to categorize polyethylene polymers is based on the presence, amount, and character of long-chain branching in the distribution of polymer molecules. Generally, long chain branches are those branches longer than branches resulting from direct incorporation of monomer. The presence of long chain branches is generally believed to relate to shrink properties of resulting films. Thus, polyethylenes without significant levels of long-chain branching have been thought to be unsuitable for use in shrink film applications.
On the other hand, polyethylenes without significant long-chain branching have been known to provide improved film properties related to MD tear resistance and dart impact strength continue to be sought. A polyethylene having an improved combination of these properties and versatility in film applications is still needed to meet performance and applications targets.
Background references are U.S. Pat. Nos. 5,382,631; 6,956,088; WO 98/26000 and WO 2012/112259.